Method and system for obtaining knowledge point implicit relationship

ABSTRACT

A method and system for obtaining a knowledge point implicit relationship are provided; first, establishing a knowledge point explicit relationship map according to knowledge point explicit relationship strengths; second, computing according to said knowledge point explicit relationship map a simple path set of two knowledge points; then, computing the implicit relationship strength values corresponding to each simple path in said simple path set; further, comparing the relationship strength values of the simple paths and setting as the significant implicit relationship strength value the simple path relationship strength having the largest value also greater than a preset threshold value. The described solution effectively avoids the problems of only using the relationship strengths between knowledge points and the ratio of relationship strengths to obtain the implicit relationship of knowledge points, the manner of searching for an implicit relationship being insufficiently accurate, and not performing normalization processing on the relationship strengths.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national application of PCT/CN2013/088740, filedon Dec. 6, 2013, which application claims a right of priority to ChinesePatent Application No. 201310456317.1, filed Sep. 29, 2013, both ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

This invention relates to a method and a system for obtaining knowledgepoint implicit relationships, and belongs to electric digital dataprocessing technology.

DESCRIPTION OF THE RELATED ART

Along with the arrival of knowledge economy, digital publication hasbecome an inevitable trend in the publication industry. Many people haveshifted from paper reading to electronic reading. A variety ofpublication resources such as electric books, magazines, digitalnewspapers contain a lot of authoritative knowledge and have highapplication value. These digital publication resources commonly spreadknowledge and information in the form of documents and articles of booksor magazines. What desired by readers is directly obtaining relativeknowledge points from these documents, but not the documents themselves,that is, finding out all relative knowledge points in the art for thepurpose of research and study.

Knowledge points have association relationships therebetween.Relationships that can be calculated directly from knowledge points andtheir explanations in the same text are referred to as “explicitrelationships”, and relationships that can be calculated indirectly fromknowledge points and their explanations in different text are referredto as “implicit relationships”. Encyclopedias as a digital publicationresource comprise concise summaries of knowledge points. Knowledgepoints in encyclopedias (entries) describe names and explanations ofknowledge points, wherein some other relative knowledge points aregenerally mentioned in the explanation portion. For example, inEncyclopedia of China—History of China, a knowledge point “Emperor QinShi Huang” is explained as “the first emperor of qin who unified chinain 221 b.c., . . . , removed the prime minister Lu Buwei, and moved himto Sichuan Province . . . , in thirty-four years of Qin Shihuang,accepted suggestions of his prime minister Li Si(some contents areomitted which are noted by . . . )”. It can be learned from theexplanation that knowledge point “Qin Shi Huang” has an associationrelationship with knowledge point “Lu Buwei”. Similarly, knowledge point“Qin Shi Huang” has an association relationship with knowledge point “LiSi”. These relationships are explicit relationship in knowledge pointsand their explanations. However, in addition to explicit relationships,a plurality of implicit relationships may be present indirectlytherebetween and implicit relationships may be more representative thanexplicit relationships. Therefore, it is necessary to further digimplicit relationships between knowledge points based on explicitrelationships of knowledge points.

In the prior art, with a method of retrieving other knowledge points inexplanation text of one knowledge point, explicit relationships betweentwo knowledge points may be easily obtained. However, indirect implicitrelationships are relationship strengths obtained depending onrelationship strength between indirect knowledge points and arelationship strength ratio, wherein the relationship strength ratiomeans a ratio of explicit relationship strength of a knowledge point toa sum of strength of all of its relative knowledge points. This methodof obtaining implicit relationship strength merely obtains implicitrelationships between knowledge points in a relative manner, instead ofanalyzing all implicit relationship strengths in a knowledge system froma perspective of the whole knowledge system, implicit relationshipstrength is obtained using explicit relationship strength betweenknowledge points and a relationship strength ratio. This implicitrelationship acquisition method may only acquire implicit relationshipsbetween knowledge points in a relative manner, resulting in insufficientaccuracy. Meanwhile, for the acquisition of explicit relationshipstrength, the explicit relationship strength is calculated based on theoccurrence number of a knowledge point in relative text segments, and nonormalization is performed for relationship strength, causing a lack ofan absolute measurable value for the determination of relationshipstrength. Thus, with the technical solution in the prior art, it isdifficult to obtain representative implicit relationships.

SUMMARY OF THE INVENTION

A technical problem to be solved in this invention is the problem ofinsufficient accuracy of implicit relationship acquisition methods inthe prior art, in which implicit relationships between knowledge pointsare only obtained based on relationship strength between knowledgepoints and a relationship strength ratio, and no normalization isperformed for relationship strength, causing a lack of an absolutemeasurable value for the determination of relationship strength andmaking it difficult to obtain representative implicit relationships.Thus, a method and system is provided for obtaining most representativeimplicit relationships based on explicit relationships of knowledgepoints in a global space.

In order to solve the above problem, the following technical solution isgiven in this invention.

A method for obtaining knowledge point implicit relationships,comprising the following steps:

establishing a graph of knowledge point explicit relationships accordingto all knowledge points and their explanations; according to the graphof knowledge point explicit relationships, calculating a set of simplepaths between two knowledge points; calculating implicit relationshipstrength corresponding to each simple path in the set of simple paths;comparing implicit relationship strength values of each simple path toset an implicit relationship strength value of a path having the largestvalue and greater than a predetermined threshold as significant implicitrelationship strength.

Optionally, the process of establishing a graph of knowledge pointexplicit relationships according to all knowledge points and theirexplanations comprises the following steps: calculating knowledge pointforward explicit relationships according to all knowledge points andtheir explanations and setting knowledge point forward explicitrelationship strength values; calculating knowledge point backwardexplicit relationships according to a set of all knowledge points andtheir explanations and setting knowledge point backward explicitrelationship strength values; according to the knowledge point forwardexplicit relationships and the knowledge point backward explicitrelationships, calculating knowledge point explicit relationships andcalculating explicit relationship strength values of the knowledgepoints; according to the explicit relationship strength values of theknowledge points, establishing a graph of knowledge point explicitrelationships.

Optionally, the method of setting knowledge point forward explicitrelationship strength comprises: if (o_(i),o_(j))∈R_(ij) ^(p), theforward explicit relationship strength from knowledge point o_(i) toknowledge point o_(j) is set to f_(p)(i,j)=0.66; if (o_(i),o_(j))∉R_(ij)^(p), the forward explicit relationship strength from knowledge pointo_(i) to knowledge point o_(j) is set to f_(p)(i,j)=0; wherein, R_(ij)^(p) represents a forward explicit relationship from o_(i) to o_(j),R_(ij) ^(p)={(o_(i),o_(j))|x_(j)∈H(y_(i)),i≠j}, x_(i) is the title ofknowledge point o_(i), y_(j) is the explanation of knowledge pointo_(i), H(y_(i)) is a set of knowledge points involved in y_(i), i, j=1,2, . . . , n (n is the number of knowledge points).

Optionally, the method of setting knowledge point backward explicitrelationship strength comprises: if (o_(i),o_(j))∈R_(ij) ^(N), thebackward explicit relationship strength value from knowledge point o_(i)to knowledge point o_(j) is set to f_(N)(i,j)=0.33; if(o_(i),o_(j))∉R_(ij) ^(N), the backward explicit relationship strengthvalue from knowledge point o_(i) to knowledge point o_(j) is set tof_(N)(i,j)=0; wherein, R_(ij) ^(N) represents a backward explicitrelationship from o_(i) to o_(j), R_(ij)^(N)={(o_(i),o_(j))|x_(i)∈H(y_(i)),i≠j}.

Optionally, the method of calculating knowledge point explicitrelationships is:R _(ij) ^(E) =R _(ij) ^(p) ∪R _(ij) ^(N)

Wherein, R_(ij) ^(E) represents an explicit relationship from knowledgepoint o_(i) to knowledge point o_(j), R_(ij) ^(N) represents a backwardexplicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(P) represents a forward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), and a set R^(E) ofexplicit relationships among all knowledge points is:R ^(E) =∪R _(ij) ^(E)

The method of calculating knowledge point explicit relationship strengthis:f _(E)(i,j)=f _(p)(i,j)+f _(N)(i,j)Wherein, f_(E)(i,j) represents the explicit relationship strength valuefrom knowledge point o_(i) to knowledge point o_(j), f_(p)(i,j)represents the forward explicit relationship strength value fromknowledge point o_(i) to knowledge point o_(j), f_(N)(i,j) representsthe backward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j);

relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E. A graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.

Optionally, the explicit relationship graph is a weighted and directedgraph G. The weighted and directed graph G comprises edges, weightvalues and vertices. Wherein, the method of setting edges and weightscomprises: a weight value of an edge from knowledge point o_(i) toknowledge point o_(j) in the weighted and directed graph G is set tof_(E)(i,j); if f_(E)(i,j)=0, there not being an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG, wherein f_(E)(i,j) represents an explicit relationship weight valuefrom knowledge point o_(i) to knowledge point o_(j); vertices of theweighted and directed graph G are the same as vertices in the explicitrelationship strength matrix E, both representing knowledge points.

Optionally, the algorithm of generating a set of simple paths betweentwo knowledge points comprises: an initial value of a set D_(ik) is setto an edge from vertex i to vertex j, if a path in the set D_(ik) isintersected with a path in a set D_(ik) at a vertex j, a simple pathfrom vertex i to vertex k is obtained through merging the two paths andis stored in the set D_(ik); wherein, i, j, k=1, 2, . . . , n (n is thenumber of vertices), all values of k, i, j are traversed in ascendingorder and are stored in the set D_(ik).

Optionally, from the set of simple paths between two knowledge points,the first k simple paths are obtained using a deletion algorithm toapproximate the set of all simple paths.

Optionally, the method of calculating implicit relationship strengthcorresponding to each simple path in the set of simple paths is:Πf_(E)(m,n), wherein (o_(m),o_(n))∈R_(mn) ^(E), f_(E)(m,n) is theimplicit relationship strength from knowledge point o_(m) to knowledgepoint o_(n), m, n represent indexes of knowledge points; (o_(m),o_(n))is an edge on the simple path.

Optionally, the predetermined threshold of implicit relationshipstrength is set to wherein 0.05≤ξ≤0.4. Preferably, the predeterminedthreshold of implicit relationship strength is ξ=0.1.

A system for obtaining knowledge point implicit relationships,comprising:

a knowledge point implicit relationship graph establishment module forestablishing a graph of knowledge point explicit relationships accordingto all knowledge points and their explanations; a simple path setcalculation module for, according to the graph of knowledge pointexplicit relationships, calculating a set of simple paths between twoknowledge points; an implicit relationship strength calculation modulefor calculating implicit relationship strength values corresponding toeach simple path in the set of simple paths; a significant implicitrelationship strength setting module for comparing implicit relationshipstrength of each simple path to set an implicit relationship strengthvalue of a path having the largest value and greater than apredetermined threshold as significant implicit relationship strength.

Optionally, the knowledge point implicit relationship graphestablishment module comprises: a knowledge point forward explicitrelationship strength setting unit for calculating knowledge pointforward explicit relationships according to a set of all knowledgepoints and their explanations and setting knowledge point forwardexplicit relationship strength values; a knowledge point backwardexplicit relationship strength setting unit for calculating knowledgepoint backward explicit relationships according to a set of allknowledge points and their explanations and setting knowledge pointbackward explicit relationship strength values; a knowledge pointexplicit relationship strength calculation unit for, according to theknowledge point forward explicit relationships and the knowledge pointbackward explicit relationships, calculating knowledge point explicitrelationships and calculating explicit relationship strength values ofthe knowledge points; an explicit relationship graph establishment unitfor, according to the explicit relationship strength of the knowledgepoints, establishing a graph of knowledge point explicit relationships.

Optionally, the method of setting knowledge point forward explicitrelationship strength values comprises: if (o_(i),o_(j))∈R_(ij) ^(p),the forward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j) is set to f_(p)(i,j)=0.66; if(o_(i),o_(j))∉R_(ij) ^(p), the forward explicit relationship strengthvalue from knowledge point o_(i) to knowledge point o_(j) is set tof_(p)(i,j)=0; wherein, R_(ij) ^(p) represents a forward explicitrelationship from o_(i) to o_(j), R_(ij)^(p)={(o_(i),o_(j))|x_(j)∈H(y_(i)),i≠j}, x_(i) is the title of knowledgepoint o_(i), y_(j) is the explanation of knowledge point o_(i), H(y_(i))is a set of knowledge points involved in y_(i), i, j=1, 2, . . . , n (nis the number of knowledge points).

Optionally, the method of setting knowledge point backward explicitrelationship strength values comprises: if (o_(i),o_(j))∈R_(ij) ^(N),the backward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j) is set to f_(N)(i,j)=0.33; if(o_(i),o_(j))∉R_(ij) ^(N), the backward explicit relationship strengthvalue from knowledge point o_(f) to knowledge point o_(i) is set tof_(N)(i,j)=0; wherein, R_(ij) ^(N) represents a backward explicitrelationship from o_(i) to o_(j), R_(ij)^(N)={(o_(i),o_(j))|x_(i)∈H(y_(i)),i≠j}.

Optionally, the method of calculating knowledge point explicitrelationships is:R _(ij) ^(E) =R _(ij) ^(p) ∪R _(ij) ^(N)

Wherein, R_(ij) ^(E) represents an explicit relationship from knowledgepoint o_(i) to knowledge point o_(j), R_(ij) ^(N) represents a backwardexplicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(P) represents a forward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), and a set R^(E) ofexplicit relationships among all knowledge points is:R ^(E) =∪R _(ij) ^(E)

The method of calculating knowledge point explicit relationship strengthis:f _(E)(i,j)=f _(p)(i,j)f _(N)(i,j)

Wherein, f_(E)(i,j) represents the explicit relationship strength fromknowledge point o_(i) to knowledge point o_(j), f_(p)(i,j) representsthe forward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j), f_(N)(i,j) represents the backwardexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j);

relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E. A graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.

Optionally, the explicit relationship graph is a weighted and directedgraph G. The weighted and directed graph G comprises edges, weightvalues and vertices. Wherein, the method of setting edges and weightscomprises: a weight value of an edge from knowledge point o_(i) toknowledge point o_(j) in the weighted and directed graph G is set tof_(E)(i,j); if f_(E)(i,j)=0, there not being an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG, wherein f_(E)(i,j) represents an explicit relationship weight valuefrom knowledge point o_(i) to knowledge point o_(j); vertices of theweighted and directed graph G are the same as vertices in the explicitrelationship strength matrix E, both representing knowledge points.

Optionally, the algorithm of generating a set of simple paths betweentwo knowledge points comprises: an initial value of a set D_(ik) is setto an edge from vertex i to vertex j, if a path in the set D_(ik) isintersected with a path in a set D_(ik) at a vertex j, a simple pathfrom vertex i to vertex k is obtained through merging the two paths andis stored in the set D_(ik); wherein, i, j, k=1, 2, . . . , n (n is thenumber of vertices), all values of k, i, j are traversed in ascendingorder and are stored in the set D_(ik).

Optionally, from the set of simple paths between two knowledge points,the first k simple paths are obtained using a deletion algorithm toapproximate the set of all simple paths.

Optionally, in the implicit relationship strength calculation module,the method of calculating implicit relationship strength valuescorresponding to each simple path in the set of simple paths is:Πf_(E)(m,n), wherein (o_(m),o_(n))∈R_(mn) ^(E), f_(E)(m,n) is theimplicit relationship strength value from knowledge point o_(m) toknowledge point o_(n), m, n represent indexes of knowledge points;(o_(m),o_(n)) is an edge on the simple path.

Optionally, the predetermined threshold of implicit relationshipstrength is set to ξ, wherein 0.05≤ξ≤0.4. Preferably, the predeterminedthreshold of implicit relationship strength is ξ=0.1.

One or more computer readable medium having stored thereoncomputer-executable instructions that when executed by a computerperform a method of obtaining knowledge point implicit relationships,the method comprising: establishing a graph of knowledge point explicitrelationships according to all knowledge points and their explanations;according to the graph of knowledge point explicit relationships,calculating a set of simple paths between two knowledge points;calculating implicit relationship strength corresponding to each simplepath in the set of simple paths; comparing implicit relationshipstrength of each simple path to set implicit relationship strength of apath having the largest value and greater than a predetermined thresholdas the most significant implicit relationship strength.

Compared with the prior art, the method of obtaining knowledge pointimplicit relationships disclosed in this disclosure has the one or moreadvantages below:

(1) the method of obtaining knowledge point implicit relationships inthis disclosure comprises the following steps: establishing a graph ofknowledge point explicit relationships according to all knowledge pointsand their explanations; according to the graph of knowledge pointexplicit relationships, calculating a set of simple paths between twoknowledge points; calculating implicit relationship strengthcorresponding to each simple path in the set of simple paths; comparingimplicit relationship strength of each simple path to set implicitrelationship strength of a path having the largest value and greaterthan a predetermined threshold as the most significant implicitrelationship strength. The above method may effectively avoid theproblem in the prior art of insufficient accuracy of the implicitrelationship acquisition method in the prior art, in which implicitrelationships between knowledge points are only obtained based onrelationship strength between knowledge points and a relationshipstrength ratio, and no normalization is performed for relationshipstrength, causing a lack of an absolute measurable value for thedetermination of relationship strength and making it difficult to obtainrepresentative implicit relationships.

(2) the method of obtaining knowledge point implicit relationships inthis disclosure is based on explicit relationships, through thenormalization of forward explicit relationships and backward explicitrelationship strength values, explicit relationship strength values areset in a range [0, 0.99] to simplify calculation; meanwhile, implicitrelationship strength values are also restricted in the range [0, 0.99]to provide an absolute measurable value used for obtaining the mostrepresentative implicit relationships based on knowledge point explicitrelationships in a global space.

(3) According the method of obtaining knowledge point implicitrelationships of this disclosure, an algorithm suggested by Frank Rubinis adopted as the algorithm for obtaining a set of simple paths betweentwo knowledge points: in the algorithm for obtaining a set of simplepaths, simple path calculation is performed by merging two paths into asimple path only if the two paths are intersected at a vertex to obtaina set of simple paths between two knowledge points. This method issimple, convenient for calculation, and is easy to implement.

(4) According the method of obtaining knowledge point implicitrelationships of this disclosure, when obtaining the set of simple pathsbetween two knowledge points, the first K simple paths are obtainedusing a deletion algorithm. The main idea of the deletion algorithm isto delete an edge from an existing path in a directed graph and search asubstitutive edge to find out a next optional simple path. With thismethod, a new vertex is obtained through expansion based on a previousset of vertices while inheriting an adjacent edge of the expandedvertex, which is suitable for finding the first K simple paths betweenknowledge points. This method is simple, convenient for calculation, andis easy to implement.

(5) According the method of obtaining knowledge point implicitrelationships of this disclosure, knowledge point explicit relationshipstrength is obtained through calculating knowledge point forwardexplicit relationship strength and backward explicit relationshipstrength. The method of evaluating relationship strength in twodirections may further improve the accuracy of knowledge point explicitrelationship strength.

(6) According the method of obtaining knowledge point implicitrelationships of this disclosure, through converting an explicitrelationship strength matrix to a weighted and directed graph, thecalculation of simple paths between knowledge points is simplified,resulting in easy algorithm implementation and improved operation speed.

(7) According the method of obtaining knowledge point implicitrelationships of this disclosure, through setting a predeterminedthreshold of implicit relationship strength, some simple paths havingweek implicit relationships may be filtered out to directly remove pathsthat are actually meaningless.

(8) With a system for obtaining knowledge point implicit relationshipsof this disclosure, using the method of obtaining knowledge pointimplicit relationships, it is possible to avoid the problem in the priorart of insufficient accuracy of the implicit relationship acquisitionmethod in the prior art, in which implicit relationships betweenknowledge points are only obtained based on relationship strengthbetween knowledge points and a relationship strength ratio, and nonormalization is performed for relationship strength, causing a lack ofan absolute measurable value for the determination of relationshipstrength and making it difficult to obtain representative implicitrelationships.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of this invention, a description will begiven with reference to the accompanying drawings, wherein:

FIG. 1 is a flowchart of a method of obtaining knowledge point implicitrelationships according to an embodiment of this disclosure;

FIG. 2 is a structure diagram of a system for obtaining knowledge pointimplicit relationships according to an embodiment of this disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment 1

A flowchart of a method of obtaining knowledge point implicitrelationships provided in this embodiment is shown in FIG. 1. Knowledgepoints discussed in this embodiment are knowledge interaction units,representing concepts or entries, such as Qin Shi Huang, Tang Dynasty,Hundred Days' Reform.

This embodiment provides a method of obtaining knowledge point implicitrelationships, which is illustrated with an example of finding knowledgepoint implicit relationships in an encyclopedia. The encyclopediacomprises documents having titles of knowledge points and explanationtext of those knowledge points. Knowledge point information contained inthe encyclopedia is defined as O={o₁, o₂, . . . , o_(n)}, wherein o_(i)(i=1, . . . , n) represents a knowledge point, a set of all knowledgepoints and their explanations is A={(x_(i),y_(i)), i=1, . . . , n}, themethod particularly comprising the following steps.

S1: establish a graph of knowledge point explicit relationshipsaccording to all knowledge points and their explanations. In a specificembodiment, the particular step is as follows:

S11: calculate knowledge point forward explicit relationships accordingto all knowledge points and their explanations, and set knowledge pointforward explicit relationship strength values.

The method of setting knowledge point forward explicit relationshipstrength values comprises:

if (o_(i),o_(j))∈R_(ij) ^(p), the forward explicit relationship strengthvalue from knowledge point o_(i) to knowledge point o_(j) is set tof_(p)(i,j)=0.66;

if (o_(i),o_(j))∉R_(ij) ^(P), the forward explicit relationship strengthvalue from knowledge point o_(i) to knowledge point o_(j) is set tof_(p)(i,j)=0;

wherein, R_(ij) ^(p) represents a forward explicit relationship fromo_(i) to o_(j), R_(ij) ^(p)={(o_(i),o_(j))|x_(j)∈H(y_(i)),i≠j}, x_(i) isthe title of knowledge point o_(i), y_(j) is the explanation ofknowledge point o_(i), H(y_(i)) is a set of knowledge points involved iny_(i), i, j=1, 2, . . . , n (n is the number of knowledge points).

S12: calculate knowledge point backward explicit relationships accordingto all knowledge points and their explanations, and set knowledge pointbackward explicit relationship strength values.

The method of setting knowledge point backward explicit relationshipstrength values comprises:

if (o_(i),o_(j))∉R_(ij) ^(N), the backward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j) isset to f_(N)(i,j)=0.33;

if (o_(i),o_(j))∈R_(ij) ^(N), the backward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j) isset to f_(N)(i,j)=0;

wherein, RN represents a backward explicit relationship from o_(i) too_(j), R_(ij) ^(N)={(o_(i),o_(j))|x_(i)∉H(y_(i)), i≠j}.

S13: calculate knowledge point explicit relationships according to theknowledge point forward explicit relationships and the knowledge pointbackward explicit relationships, and calculate knowledge point explicitrelationship strength values.

The method of calculating knowledge point explicit relationships is:R _(ij) ^(E) =R _(ij) ^(P) ∪R _(ij) ^(N)

Wherein, R_(ij) ^(E) represents an explicit relationship from knowledgepoint o_(i) to knowledge point o_(j), R_(ij) ^(N) represents a backwardexplicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(P) represents a forward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), and a set R^(E) ofexplicit relationships among all knowledge points is:R ^(E) =∪R _(ij) ^(E)The method of calculating knowledge point explicit relationship strengthvalues is:f _(E)(i,j)=f _(p)(i,j)+f _(N)(i,j)

Wherein, f_(E)(i,j) represents the explicit relationship strength valuefrom knowledge point o_(i) to knowledge point o_(j), f_(p)(i,j)represents the forward explicit relationship strength value fromknowledge point o_(i) to knowledge point o_(j), f_(N)(i,j) representsthe backward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j);

According to the method of obtaining knowledge point implicitrelationships, knowledge point explicit relationship strength isobtained through calculating knowledge point forward explicitrelationship strength and backward explicit relationship strength. Themethod of evaluating relationship strength in two directions may furtherimprove the accuracy of knowledge point explicit relationship strength.

Relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E. A graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.

According to the method of obtaining knowledge point implicitrelationships in this embodiment, based on explicit relationships,through the normalization of forward explicit relationships and backwardexplicit relationship strength, explicit relationship strength valuesare set in a range [0, 0.99] to simplify calculation; meanwhile,implicit relationship strength values are also restricted in the range[0, 0.99] to provide an absolute measurable value used for obtaining themost representative implicit relationships based on knowledge pointexplicit relationships in a global space.

S14: according to the explicit relationship strength of the knowledgepoints, establish a graph of knowledge point explicit relationships. Theexplicit relationship graph is a weighted and directed graph G,comprising edges, weights and vertices, wherein,

the method of setting edges and weights comprises:

a weight value of an edge from knowledge point o_(i) to knowledge pointo_(j) in the weighted and directed graph G is set to f_(E)(i,j); iff_(E)(i,j)=0, there not being an edge from knowledge point o_(i) toknowledge point o_(j) in the weighted and directed graph G, whereinf_(E)(i,j) represents an explicit relationship weight value fromknowledge point o_(i) to knowledge point o_(j);

vertices of the weighted and directed graph G are the same as verticesin the explicit relationship strength matrix E, both representingknowledge points.

The weighted and directed graph G is an assistant graph used forcalculating simple paths. Through converting the explicit relationshipstrength matrix to a weighted and directed graph, the calculation ofsimple paths between knowledge points is simplified, resulting in easyalgorithm implementation and improved operation speed.

S2: according to the graph of knowledge point explicit relationships,calculate a set of simple paths between two knowledge points. Analgorithm suggested by Frank Rubin is adopted as the algorithm forobtaining a set of simple paths between two knowledge points (see FrankRubin. Enumerating all simple paths in a graph[J]. IEEE Transactions onCircuits and Systems, 1978, 25(8):641-642 for details).

An initial value of a set D_(ik) is set to an edge from vertex i tovertex j, if a path in the set D_(ik) is intersected with a path in aset D_(ik) at a vertex j, a simple path from vertex i to vertex k isobtained through merging the two paths and is stored in the set D_(ik).This method is simple, convenient for operations and is easy toimplement. Wherein, i, j, k=1, 2, . . . , n (n is the number ofvertices), all values of k, i, j are traversed in ascending order andare stored in the set D_(ik). All simple paths from vertex i to vertex kare stored in the set D_(ik).

A simple path p_(ij)=

o_(i)=o₁′, o₂′, . . . , o_(l−1)′, o_(l)′=o_(j)

from knowledge point o_(f) to knowledge point o_(i) comprises apotential relationship between these knowledge points, which reveals animplicit relationship from knowledge point o_(i) to knowledge pointo_(j) in one dimension, wherein for all knowledge point relationships onpath p_(ij), the set thereof S_(ij)={(o_(i),o₂′), (o_(l−1)′o_(j)),(o_(k)′o_(k+1)′)|k=2, . . . , l−2}⊆R^(E), i.e., all knowledge pointrelationships on path p_(ij) are explicit relationships, the number ofsimple paths from knowledge point o_(i) to knowledge point o_(j) isequal to or greater than zero; if the number of simple paths is zero, itindicates there is not any implicit relationship between knowledge pointo_(i) to knowledge point o_(j).

In the algorithm for obtaining a set of simple paths, simple pathcalculation is performed by merging two paths into a simple path only ifthe two paths are intersected at a vertex to obtain a set of simplepaths between two knowledge points. This method is simple, convenientfor calculation, and is easy to implement.

S3: calculate implicit relationship strength values corresponding toeach simple path in the set of simple paths.

The method of calculating implicit relationship strength valuescorresponding to each simple path in the set of simple paths is:Πf_(E)(m,n), wherein (o_(m),o_(n))∈R_(mn) ^(E), f_(E)(m,n) is theimplicit relationship strength value from knowledge point o_(m) toknowledge point o_(n), m, n represent indexes of knowledge points;(o_(m)o_(n)) is an edge on the simple path.

S4: compare implicit relationship strength values of each simple path toset implicit relationship strength value of a path having the largestvalue and greater than a predetermined threshold as the most significantimplicit relationship strength. In an embodiment, the predeterminedimplicit relationship strength threshold is set to ξ, wherein0.05≤ξ≤0.4. Preferably, the implicit relationship strength threshold isξ=0.1. That is, the implicit relationship strength value from knowledgepoint o_(i) to knowledge point o_(j) is set to the largest value ofimplicit relationship strength corresponding to the simple path, and theimplicit relationship strength value of a path having f_(I)(i,j)>0.1 isset the most significant implicit relationship strength.

In other alternative embodiments, the predetermined implicitrelationship strength threshold ξ may be set to 0.15, 0.2, 0.3, 0.4 andother different values selected according to demands of users or theobtained implicit relationship strength.

Through setting a predetermined threshold of implicit relationshipstrength, some simple paths having week implicit relationships may befiltered out to directly remove paths that are actually meaningless.

Embodiment 2

Except for step S3 of this embodiment, other steps are the same as thatin embodiment 1. Step S3: according to the graph of knowledge pointexplicit relationships, calculate a set of simple paths between twoknowledge points.

In step S3, an algorithm suggested by Frank Rubin is adopted as thealgorithm for obtaining a set of simple paths between two knowledgepoints (see Frank Rubin. Enumerating all simple paths in a graph[J].IEEE Transactions on Circuits and Systems, 1978, 25(8):641-642 fordetails).

A simple path p_(ij)=

o_(i)=o₁′, o₂′, . . . , o_(l−1)′, o_(l)′=o_(j)

from knowledge point o_(i) to knowledge point o_(j) comprises apotential relationship between these knowledge points, which reveals animplicit relationship from knowledge point o_(i) to knowledge pointo_(j) in one dimension, wherein for (all knowledge point relationshipson path p_(ij), the set thereof S_(ij)={(o_(i),o₂′), (o_(l−1)′o_(j)),(o_(k)′o_(k+1)′)|k=2, . . . , l−2}⊆R^(E), i.e., all knowledge pointrelationships on path p_(ij) are explicit relationships, the number ofsimple paths from knowledge point o_(i) to knowledge point o_(j) isequal to or greater than zero; if the number of simple paths is zero, itindicates there is not any implicit relationship between knowledge pointo_(i) to knowledge point o_(j).

The main idea of the deletion algorithm is to delete an edge from anexisting path in a directed graph and search a substitutive edge to findout a next optional simple path. With this method, a new vertex isobtained through expansion based on a previous set of vertices whileinheriting an adjacent edge of the expanded vertex, which is suitablefor finding the first K simple paths between knowledge points. Thismethod is simple, convenient for calculation, and is easy to implement.

The method of obtaining knowledge point implicit relationships in thisembodiment comprises the following steps: establishing a graph ofknowledge point explicit relationships according to explicitrelationship strength of knowledge points; according to the graph ofknowledge point explicit relationships, calculating a set of simplepaths between two knowledge points; calculating implicit relationshipstrength corresponding to each simple path in the set of simple paths;comparing implicit relationship strength of each simple path to setimplicit relationship strength of a path having the largest value andgreater than a predetermined threshold as the most significant implicitrelationship strength. The above method may effectively avoid theproblem in the prior art of insufficient accuracy of the implicitrelationship acquisition method in the prior art, in which implicitrelationships between knowledge points are only obtained based onrelationship strength between knowledge points and a relationshipstrength ratio, and no normalization is performed for relationshipstrength, causing a lack of an absolute measurable value for thedetermination of relationship strength and making it difficult to obtainrepresentative implicit relationships.

Embodiment 3

FIG. 2 is a structure diagram of a system for obtaining knowledge pointimplicit relationships according to an embodiment of this disclosure.The system for obtaining knowledge point implicit relationships providedin this embodiment comprises: a knowledge point implicit relationshipgraph establishment module 21 for establishing a graph of knowledgepoint explicit relationships according to all knowledge points and theirexplanations; a simple path set calculation module 22 for, according tothe graph of knowledge point explicit relationships, calculating a setof simple paths between two knowledge points; an implicit relationshipstrength calculation module 23 for calculating implicit relationshipstrength values corresponding to each simple path in the set of simplepaths; a significant implicit relationship strength setting module 24for comparing implicit relationship strength values of each simple pathto set the implicit relationship strength value of a path having thelargest value and greater than a predetermined threshold as significantimplicit relationship strength.

In one embodiment, the knowledge point implicit relationship graphestablishment module 21 comprises a knowledge point forward explicitrelationship strength setting unit 211 for calculating knowledge pointforward explicit relationships according to a set of all knowledgepoints and their explanations and setting knowledge point forwardexplicit relationship strength values; a knowledge point backwardexplicit relationship strength setting unit 212 for calculatingknowledge point backward explicit relationships according to a set ofall knowledge points and their explanations and setting knowledge pointbackward explicit relationship strength values; a knowledge pointexplicit relationship strength calculation unit 213 for, according tothe knowledge point forward explicit relationships and the knowledgepoint backward explicit relationships, calculating knowledge pointexplicit relationships and calculating explicit relationship strengthvalues of the knowledge points; an explicit relationship graphestablishment unit 214 for, according to the explicit relationshipstrength values of the knowledge points, establishing a graph ofknowledge point explicit relationships.

The method of setting knowledge point forward explicit relationshipstrength values comprises: if (o_(i),o_(j))∈R_(ij) ^(p), the forwardexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j) is set to f_(p)(i,j)=0.66; if (o_(i),o_(j))∉R_(ij)^(p), the forward explicit relationship strength value from knowledgepoint o_(i) to knowledge point o_(j) is set to f_(p)(i,j)=0; wherein,R_(ij) ^(p) represents a forward explicit relationship from o_(i) too_(j), R_(ij) ^(p)={(o_(i),o_(j))|x_(j)∈H (y_(i)),i≠j}, x_(i) is thetitle of knowledge point o_(i), y_(j) is the explanation of knowledgepoint o_(i), H(y_(i)) is a set of knowledge points involved in y_(j), i,j=1, 2, . . . , n (n is the number of knowledge points).

The method of setting knowledge point backward explicit relationshipstrength values comprises: if (o_(i),o_(j))∈R_(ij) ^(N), the backwardexplicit relationship strength from knowledge point o_(i) to knowledgepoint o_(j) is set to f_(N)(i,j)=0.33; if (o_(i),o_(j))∉R_(ij) ^(N), thebackward explicit relationship strength from knowledge point o_(i) toknowledge point o_(j) is set to f_(N)(i,j)=0; wherein, R_(ij) ^(N)represents a backward explicit relationship from o_(i) to o_(j), R_(ij)^(N)={(o_(i),o_(j))|x_(i)∈H(y_(i)),i≠j}.

The method of calculating knowledge point explicit relationships is:R _(ij) ^(E) =R _(ij) ^(p) ∪R _(ij) ^(N)

Wherein, R_(ij) ^(E) represents an explicit relationship from knowledgepoint o_(i) to knowledge point o_(j), R_(ij) ^(N) represents a backwardexplicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(P) represents a forward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), and a set R^(E) ofexplicit relationships among all knowledge points is:R ^(E) =∪R _(ij) ^(E)

The method of calculating knowledge point explicit relationship strengthis:f _(E)(i,j)=f _(p)(i,j)f _(N)(i,j)

Wherein, f_(E)(i,j) represents the explicit relationship strength valuefrom knowledge point o_(i) to knowledge point o_(j), f_(p)(i,j)represents the forward explicit relationship strength value fromknowledge point o_(i) to knowledge point o_(j), f_(N)(i,j) representsthe backward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j);

relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E. A graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.

The explicit relationship graph is a weighted and directed graph G. Theweighted and directed graph G comprises edges, weight values andvertices. Wherein, the method of setting edges and weights comprises: aweight value of an edge from knowledge point o_(i) to knowledge pointo_(j) in the weighted and directed graph G is set to f_(E)(i,j); iff_(E)(i,j)=0, there not being an edge from knowledge point o_(f) toknowledge point o_(i) in the weighted and directed graph G, whereinf_(E)(i,j) represents an explicit relationship weight value fromknowledge point o_(i) to knowledge point o_(j); vertices of the weightedand directed graph G are the same as vertices in the explicitrelationship strength matrix E, both representing knowledge points.

In this embodiment, the algorithm of generating a set of simple pathsbetween two knowledge points comprises: an initial value of a set D_(ik)is set to an edge from vertex i to vertex j, if a path in the set D_(ik)is intersected with a path in a set D_(ik) at a vertex j, a simple pathfrom vertex i to vertex k is obtained through merging the two paths andis stored in the set D_(ik); wherein, i, j, k=1, 2, . . . , n (n is thenumber of vertices), all values of k, i, j are traversed in ascendingorder and are stored in the set D_(ik).

As an alternative embodiment, from the set of simple paths between twoknowledge points, the first k simple paths are obtained using a deletionalgorithm to approximate the set of all simple paths.

In the implicit relationship strength calculation module, the method ofcalculating implicit relationship strength values corresponding to eachsimple path in the set of simple paths is: Πf_(E)(m,n), wherein(o_(m),o_(n))∈R_(mn) ^(E), f_(E) (m,n) is the implicit relationshipstrength value from knowledge point o_(m) to knowledge point o_(n), m, nrepresent indexes of knowledge points; (o_(m)o_(n)) is an edge on thesimple path.

The predetermined threshold of implicit relationship strength is set toξ, wherein 0.05≤ξ≤0.4. Preferably, the predetermined threshold ofimplicit relationship strength is ξ=0.1.

A system for obtaining knowledge point implicit relationships isprovided in this embodiment, using the method of obtaining knowledgepoint implicit relationships, it is possible to avoid the problem in theprior art of insufficient accuracy of the implicit relationshipacquisition method in the prior art, in which implicit relationshipsbetween knowledge points are only obtained based on relationshipstrength between knowledge points and a relationship strength ratio, andno normalization is performed for relationship strength, causing a lackof an absolute measurable value for the determination of relationshipstrength and making it difficult to obtain representative implicitrelationships.

Embodiment 4

An application example is provided in this embodiment.

There is an explicit relationship between Qin ShiHuang and Li Si, whichhas an explicit relationship strength value of 0.5. This relationship isa directed edge e1 from Qin ShiHuang to Li Si, with a weight value of0.5. There is an explicit relationship between Li Si and Han Fei, whichhas an explicit relationship strength value of 0.3, which is representedas a directed edge e1 from Li SiHuang to Han Fei with a weight value of0.5 in the diagram.

Based on the above information, a simple path from Qin ShiHuang to HanFei is obtained, the simple path starting from Qin ShiHuang, passingthrough e1, Li Si, and ending at Han Fei. This simple path represents animplicit relationship from Qin ShiHuang to Han Fei, with implicitrelationship strength of 0.5*0.3=0.15.

Implicit relationship strength values corresponding to other simplepaths between Qin ShiHuang and Han Fei may be obtained throughcalculation. For example, other two simple paths correspond to implicitrelationship strength of 0.1 and 0.12 respectively. Setting ξ=0.1, thesignificant implicit relationship strength from Qin ShiHuang to Han Feiis 0.15.

Obviously, the above embodiments are merely examples given for cleardescription, but not limitations of this invention. For those skilled inthe art, other modifications or variations may be made based on theabove description, which will not be and cannot be listed exhaustivelyherein. These apparent modifications or variations derived are stillwithin the protection scope of this invention.

Those skilled in the art should understand that the embodiments of thisapplication can be provided as method, system or products of computerprograms. Therefore, this application can use the forms of entirelyhardware embodiment, entirely software embodiment, or embodimentcombining software and hardware. Moreover, this application can use theform of the product of computer programs to be carried out on one ormultiple storage media (including but not limit to disk memory, CD-ROM,optical memory etc.) comprising programming codes that can be executedby computers.

This application is described with reference to the method, equipment(system) and the flow charts and/or block diagrams of computer programproducts according to the embodiments of the present invention. Itshould be understood that each flow and/or block in the flowchart and/orblock diagrams as well as the combination of the flow and/or block inthe flowchart and/or block diagram can be achieved through computerprogram commands Such computer program commands can be provided togeneral computers, special-purpose computers, embedded processors or anyother processors of programmable data processing equipment so as togenerate a machine, so that a device for realizing one or multiple flowsin the flow diagram and/or the functions specified in one block ormultiple blocks of the block diagram is generated by the commands to beexecuted by computers or any other processors of the programmable dataprocessing equipment.

Such computer program commands can also be stored in readable memory ofcomputers which can lead computers or other programmable data processingequipment to working in a specific style so that the commands stored inthe readable memory of computers generate the product of command device;such command device can achieve one or multiple flows in the flowchartand/or the functions specified in one or multiple blocks of the blockdiagram.

Such computer program commands can also be loaded on computers or otherprogrammable data processing equipment so as to carry out a series ofoperation steps on computers or other programmable equipment to generatethe process to be achieved by computers, so that the commands to beexecuted by computers or other programmable equipment achieve the one ormultiple flows in the flowchart and/or the functions specified in oneblock or multiple blocks of the block diagram.

Although preferred embodiments of this application are alreadydescribed, once those skilled in the art understand basic creativeconcept, they can make additional modification and alteration for theseembodiments. Therefore, the appended claims are intended to beinterpreted as encompassing preferred embodiments and all themodifications and alterations within the scope of this application.

What is claimed is:
 1. A method for obtaining knowledge point implicitrelationships executed by a computer, the method comprises the followingsteps: calculating knowledge point forward explicit relationshipsaccording to all knowledge points and their explanations and settingknowledge point forward explicit relationship strength values;calculating knowledge point backward explicit relationships according toa set of all knowledge points and their explanations and settingknowledge point backward explicit relationship strength values;according to the knowledge point forward explicit relationships and theknowledge point backward explicit relationships, calculating knowledgepoint explicit relationships and calculating explicit relationshipstrength values of the knowledge points; according to the explicitrelationship strength values of the knowledge points, establishing agraph of knowledge point explicit relationships; calculating a set ofsimple paths between two knowledge points according to the graph ofknowledge point explicit relationships; calculating implicitrelationship strength values corresponding to each simple path in theset of simple paths; and comparing the implicit relationship strengthvalues of each simple path to set an implicit relationship strengthvalue of a path having the largest value and greater than apredetermined threshold as significant implicit relationship strength.2. The method for obtaining knowledge point implicit relationshipsaccording to claim 1, characterized in that the method of settingknowledge point forward explicit relationship strength values comprises:if (o_(i),o_(j))∈R_(ij) ^(p), setting the forward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j) tof_(p)(i,j)=0.66; if (o_(i),o_(j))∉R_(ij) ^(p), setting the forwardexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j) to f_(p)(i,j)=0; wherein, R_(ij) ^(p), representsa forward explicit relationship from o_(i) to o_(j), R_(ij)^(p)={(o_(i),o_(j))|x_(j)∈H(y_(i)),i≠j}, x_(i) is the title of knowledgepoint o_(i), y_(i) is the explanation of knowledge point o_(i), is a setof knowledge points involved in y_(i), i, j=1, 2, . . . , n (n is thenumber of knowledge points); and/or the method of setting knowledgepoint backward explicit relationship strength values comprises: if(o_(i),o_(j))∈R_(ij) ^(N), setting the backward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j) tof_(N)(i,j)=0.33; if (o_(i),o_(j))∉R_(ij) ^(N), setting the backwardexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j) to f_(N)(i,j)=0; wherein, R_(ij) ^(N) represents abackward explicit relationship from o_(i) to o_(j), R_(ij)^(N)={(o_(i),o_(j))|x_(i)∈H(y_(i)),i≠j}.
 3. The method for obtainingknowledge point implicit relationships according to claim 1,characterized in that the method of calculating knowledge point explicitrelationships is:R _(ij) ^(E) =R _(ij) ^(p) ∪R _(ij) ^(N) Wherein, R_(ij) ^(E) representsan explicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(N) represents a backward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), R_(ij) ^(p) represents aforward explicit relationship from knowledge point o_(i) knowledge pointo_(j), and a set R^(E) of explicit relationships among all knowledgepoints is:R ^(E) =∪R _(ij) ^(E) the method of calculating knowledge point explicitrelationship strength values is:f _(E)(i,j)=f _(p)(i,j)+f _(N)(i,j) wherein, f_(E)(i,j) represents theexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j), f_(p)(i,j) represents the forward explicitrelationship strength value from knowledge point o_(i) to knowledgepoint o_(j), F_(N)(i,j) represents the backward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j);relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E; a graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.
 4. The method for obtaining knowledge point implicitrelationships according to claim 1, characterized in that the explicitrelationship graph is a weighted and directed graph G comprising edges,weight values and vertices, wherein, the method of setting edges andweights comprises: setting a weight value of an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG to f_(E)(i,j); if f_(E)(i,j)=0, there not being an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG, wherein f_(E)(i,j) represents an explicit relationship weight valuefrom knowledge point o_(i) to knowledge point o_(j); vertices of theweighted and directed graph G are the same as vertices in the explicitrelationship strength matrix E, both representing knowledge points. 5.The method for obtaining knowledge point implicit relationshipsaccording to claim 1, characterized in that the algorithm of generatinga set of simple paths between two knowledge points comprises: setting aninitial value of a set D_(ik) to an edge from vertex i to vertex j; if apath in the set D_(ik) is intersected with a path in a set D_(jk) at avertex j, merging the two paths to obtain a simple path from vertex i tovertex k and storing the simple path in the set D_(ik); wherein, i, j,k=1, 2, . . . , n (n is the number of vertices), all values of k, i, jare traversed in ascending order and are stored in the set D_(ik). 6.The method for obtaining knowledge point implicit relationshipsaccording to claim 1, characterized in that, from the set of simplepaths between two knowledge points, the first k simple paths areobtained using a deletion algorithm to approximate the set of all simplepaths.
 7. The method for obtaining knowledge point implicitrelationships according to claim 1, characterized in that the method ofcalculating implicit relationship strength values corresponding to eachsimple path in the set of simple paths is: Πf_(E)(m,n), wherein(o_(m),o_(n))∈R_(mn) ^(E), f_(E)(m,n) is the implicit relationshipstrength value from knowledge point o_(m) to knowledge point o_(n), m, nrepresent indexes of knowledge points; (o_(m), o_(n)) is an edge on thesimple path.
 8. The method for obtaining knowledge point implicitrelationships according to claim 1, characterized in that thepredetermined threshold of implicit relationship strength is set to ξ,wherein 0.05≤ξ≤0.4, preferably, the predetermined threshold of implicitrelationship strength is ξ=0.1.
 9. A system for obtaining knowledgepoint implicit relationships in a computer, the system comprises: aknowledge point implicit relationship graph comprising: a knowledgepoint forward explicit relationship strength setting unit forcalculating knowledge point forward explicit relationships according toa set of all knowledge points and their explanations and settingknowledge point forward explicit relationship strength values; aknowledge point backward explicit relationship strength setting unit forcalculating knowledge point backward explicit relationships according toa set of all knowledge points and their explanations and settingknowledge point backward explicit relationship strength values; aknowledge point explicit relationship strength calculation unit for,according to the knowledge point forward explicit relationships and theknowledge point backward explicit relationships, calculating knowledgepoint explicit relationships and calculating explicit relationshipstrength values of the knowledge points; an explicit relationship graphestablishment unit for, according to the explicit relationship strengthvalues of the knowledge points, establishing a graph of knowledge pointexplicit relationships; a simple path set calculation module for,according to the graph of knowledge point explicit relationships,calculating a set of simple paths between two knowledge points; animplicit relationship strength calculation module for calculatingimplicit relationship strength values corresponding to each simple pathin the set of simple paths; and a significant implicit relationshipstrength setting module for comparing implicit relationship strengthvalues of each simple path to set implicit relationship strength of apath having the largest value and greater than a predetermined thresholdas significant implicit relationship strength.
 10. The system forobtaining knowledge point implicit relationships according to claim 9,characterized in that the method of setting knowledge point forwardexplicit relationship strength by the knowledge point forward explicitrelationship strength setting unit comprises: if (o_(i),o_(j))∈R_(ij)^(p), setting the forward explicit relationship strength value fromknowledge point o_(i) to knowledge point o_(j) to f_(p)(i,j)=0.66; if(o_(i),o_(j))∉R_(ij) ^(p), setting the forward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j) tof_(p)(i,j)=0; wherein, R_(ij) ^(p) represents a forward explicitrelationship from o_(i) to o_(j), R_(ij)^(p)={(o_(i),o_(j))|x_(j)∈H(y_(i)),i≠j}, x_(i) is the title of knowledgepoint o_(i), y_(i) is the explanation of knowledge point o_(i), H(y_(i))is a set of knowledge points involved in y_(i), i, j=1, 2, . . . , n (nis the number of knowledge points), and/or the method of settingknowledge point backward explicit relationship strength values by theknowledge point backward explicit relationship strength setting unitcomprises: if (o_(i),o_(j))∈R_(ij) ^(N), setting the backward explicitrelationship strength value from knowledge point o_(i) to knowledgepoint o_(j), to f_(N)(i,j)=0.33; if (o_(i),o_(j))∉R_(ij) ^(N), settingthe backward explicit relationship strength value from knowledge pointo_(i) to knowledge point o_(j) to f_(N)(i,j)=0; wherein, R_(ij) ^(N)represents a backward explicit relationship from o_(i) to o_(j), R_(ij)^(N)={(o_(i),o_(j))|x_(i)∈H(y_(i)),i≠j}.
 11. The system for obtainingknowledge point implicit relationships according to claim 9,characterized in that the method of calculating knowledge point explicitrelationships by the knowledge point explicit relationship strengthcalculation unit is:R _(ij) ^(E) =R _(ij) ^(p) ∪R _(ij) ^(N) Wherein, R_(ij) ^(E) representsan explicit relationship from knowledge point o_(i) to knowledge pointo_(j), R_(ij) ^(N) represents a backward explicit relationship fromknowledge point o_(i) to knowledge point o_(j), R_(ij) ^(p) represents aforward explicit relationship from knowledge point o_(i) to knowledgepoint o_(i), and a set R^(E) of explicit relationships among allknowledge points is:R ^(E) =∪R _(ij) ^(E) the method of calculating knowledge point explicitrelationship strength values is:f _(E)(i,j)=f _(p)(i,j)+f _(N)(i,j) wherein, f_(E)(i,j) represents theexplicit relationship strength value from knowledge point o_(i) toknowledge point o_(j), f_(p)(i,j) represents the forward explicitrelationship strength value from knowledge point o_(i) to knowledgepoint o_(j), F_(N)(i,j) represents the backward explicit relationshipstrength value from knowledge point o_(i) to knowledge point o_(j);relationship strength values are calculated for all knowledge points inthe set of explicit relationships R^(E) and are stored in an explicitrelationship strength matrix E; a graph of knowledge point explicitrelationships is generated according to the explicit relationshipstrength matrix E.
 12. The system for obtaining knowledge point implicitrelationships according to claim 9, characterized in that the explicitrelationship graph is a weighted and directed graph G, comprising edges,weight values and vertices, wherein, the method of setting edges andweights comprises: setting a weight value of an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG to f_(E)(i,j); if f_(E)(i,j)=0, there not being an edge from knowledgepoint o_(i) to knowledge point o_(j) in the weighted and directed graphG, wherein f_(E)(i,j) represents an explicit relationship weight valuefrom knowledge point o_(i) to knowledge point o_(j); vertices of theweighted and directed graph G are the same as vertices in the explicitrelationship strength matrix E, both representing knowledge points. 13.The system for obtaining knowledge point implicit relationshipsaccording to claim 9, characterized in that the algorithm of generatinga set of simple paths between two knowledge points by the simple pathset calculation module comprises: setting an initial value of a setD_(ik) to an edge from vertex i to vertex j; if a path in the set D_(ik)is intersected with a path in a set D_(ik) at a vertex j, obtaining asimple path from vertex i to vertex k through merging the two paths andstoring the simple path in the set D_(ik); wherein, i, j, k=1, 2, . . ., n (n is the number of vertices), all values of k, i, j are traversedin ascending order and are stored in the set D_(ik).
 14. The system forobtaining knowledge point implicit relationships according to claim 9,characterized in that, from the set of simple paths between twoknowledge points, the first k simple paths are obtained using a deletionalgorithm to approximate the set of all simple paths.
 15. The system forobtaining knowledge point implicit relationships according to claim 9,characterized in that the method of calculating implicit relationshipstrength corresponding to each simple path in the set of simple paths bythe implicit relationship strength calculation module is: Πf_(E)(m,n), awherein (o_(m),o_(n))∈R_(mn) ^(E), f_(E)(m,n) is the implicitrelationship strength value from knowledge point o_(m) to knowledgepoint o_(n), n represent indexes of knowledge points; (o_(m),o_(n)) isan edge on the simple path.
 16. The system for obtaining knowledge pointimplicit relationships according to claim 9, characterized in that thepredetermined threshold of implicit relationship strength is set towherein ξ, 0.05≤ξ≤0.4, Preferably, the predetermined threshold ofimplicit relationship strength is ξ=0.1.
 17. One or more non-transitorycomputer readable mediums having stored thereon computer-executableinstructions that when executed by a computer perform a method ofobtaining knowledge point implicit relationships, the method comprising:calculating knowledge point forward explicit relationships according toall knowledge points and their explanations and setting knowledge pointforward explicit relationship strength values; calculating knowledgepoint backward explicit relationships according to a set of allknowledge points and their explanations and setting knowledge pointbackward explicit relationship strength values; according to theknowledge point forward explicit relationships and the knowledge pointbackward explicit relationships, calculating knowledge point explicitrelationships and calculating explicit relationship strength values ofthe knowledge points; according to the explicit relationship strengthvalues of the knowledge points, establishing a graph of knowledge pointexplicit relationships; according to the graph of knowledge pointexplicit relationships, calculating a set of simple paths between twoknowledge points; calculating implicit relationship strengthcorresponding to each simple path in the set of simple paths; comparingimplicit relationship strength values of each simple path to setimplicit relationship strength value of a path having the largest valueand greater than a predetermined threshold as the most significantimplicit relationship strength.